Traveling wave electron discharge device



tional'Telephone and Telegraph Corporation, Nutley, NJ., a corporation of Maryland Appiication'ranuary 6, 195s, serial Nar/01,211

16 claims. (Crais-'3.6)

This invention relates/to travelingv wave electron idischai-ge devices and more particularly to vslow wave propagating structures employed in relatively high power travel! ofand to extend a portion ofthe low power transmising wave electron dischargedevices.

The usualslow wave propagating structure employed in traveling wavejtubes to reduce the phase velocity of wave 'energy to approximately the phase velocity of the electron 'beam' is a helical-type transmission line. This helical-,type slow wave structure enables the successful amplification of wave energy by synchronous interchange of energy between the electron beam yand the wave energy.` However, it is now well known that thev power handling capabilities of a helix are limited since an attempt to increase the power output of a helix traveling atenft" wave tube `results in increased vheating vof the helical propagating structure due to resistive losses and, hence,v

an increase in impedance of the helical propagating structure." .Thispincreased impedance of the helical propagating lstructure reduces the gain of the device and hence places a limit on the possible power output from this typeltravelingwave tube. Due to the limited power handling capabilities, the helical propagating structure has become known asa relatively'low power slow `wave propagating structure.

Since it is desirable to obtain power output of atraveling wave tube well beyond the eicient power output possible with a helical-type traveling wave tube, loaded waveguide transmissionlines are now being employed as the slow wave propagating structure for high power traveling wave tubes since these transmission lines have relatively high power handling capabilities. 'Although this type of slow wave propagating structure is a solution 'to obtain' `increased power output `over thatobtainable with a helical-type structure -it is necessary torincrease the length and diameter of the tube structurev since the gain per unit length of a loaded waveguide is less than'the gain per'unit length of a helix, and the loaded waveguide is inherently greater in diameter. The increased length A'feature ofY this invention is the provision ofk a composite slow wave propagating structure comprising a slow q wasesinar Mar., si, i969 wave transmission line of relatively low power handling f A v capabilitiesLsuch as a helical transmission line, a slow wave transmission 'line of relatively high power handling capabilities, such as a loaded waveguide transmission line,`

fand means to couple the wave energy between said low power transmission line and'said high'power transmission ,line. j Another feature yof this invention is todisposeth .wave energy attenuation adjacent the area where wave energy is coupled from one component to t'heother component of the composite slow wave propagating structure.,

`Anotherfjfeature' of this invention is to dispose the Y.wave energy attenuation solely adjacent the low power` transmission line in juxtaposition to the output end theresion line into the high power transmission line for excitationvthereofwith energy on said low power transmission line.

` A further feature of th'is invention is to dispose the signal wave'attenuation material `at the output of the v lowpower transmission line and at the input of the high power transmission line and to couple energy-from the ylow'powe'r,transmission line to the high power transtnisl lsion lineljfby means of the electron beam which is in-interacting' relation .with thecomposite slow wave propa-v gating structure.

Still ya' further feature of this invention is the p'ro-` f. vision'iof` a counterwound helix as the low power transy mission line andan iris-loaded waveguide as the high power transmission line. l

The above-mentioned and other objects and features of this invention will become more apparent by reference to the following description taken in conjunction with `slow wave propagating structure in accordance with the.

and diameter of the resultant priory art high power traveling'wave tube are objectionable because of increase tube size and longer and larger magnetic structures for beam focusing in theregion of the slow wave propagating structure. In addition manufacture of a loaded waveguide slow wave propagating structure is expensive relative to a helical type structure. j A

Therefore, it is yzin-object of this invention to provide an improved high power slow wave propagating structure for'use in a traveling wave tube.

Another object of this invention is to provide a slow Wave propagating structure of relatively high power handling capabilities having decreased manufacturing cost. f

Still another object of this invention is to provide a slow wave propagating structure for a traveling wave tube whichv has a power handling capability substantially the same asa loaded waveguide slow wave propagating structure but which is shorter in length and lighter than 4the loadedwaveguide structure.

principles of Vthis invention.

Referring to Fig. 1, a traveling wave tube is illustrated as including therein one form of slow wave propagating structure'following/the principles of this invention. The

tube includes a vacuum envelope 1 composed of metal, i

a collector electrode 2 disposed at one end of envelope 1 and an electron gun 3 disposed at the other end of `envelope 1 for4v projecting an electron beam along a given path 4 to collector electrode 2. A magnetic focusing 'arrangement 5 is disposed coaxial of path 4 to maintain the electrons of the beam focused throughout its travel from gun 3 to electrode 2. Arrangement 5 is illustrated as an electromagnet, but it is to be understood that' a permanent magnet may be substituted therefor'.V

Ay composite slow propagating structure 6 is disposed in juxtaposition to path 4 to enable linteraction between;-

the electron beamflowng along path 4 and the wavel energy propagated on structure 6 at substantially the same phasevelocity as the electrons of the electron beam.

In accordance with this invention, composite structure.

6 includes a low power slow wave transmission line illusfLQ-T trated as being a helical-type transmission line 7 and "a high powerslowwave transmission line illustrated.l asflv being an iris-loaded waveguide'transmission line 8.-'It

is to be understood that any loadedwaveguide Will be suitable as the high power portion ofthe composite slow,

wave structure 6. It is to be further .understooc'ls'that'v the electron beam'may be an annular'beam tofbo'in 3 v interacting -relationl with't'he wave energy on a loaded waveguide``such 'as a disc-loaded waveguide. Helical transmission line may be supported by dielectricrods 9 which are .positioned at one .endthereof .by member 10 4 Y walls of the first section thereof to absorb any waves reected from the'output load. Y Y

While I have described above the principles of my invention in connection with specific apparatus, it is to disposed transversely of envelope l having mountedtheref be clearly understood that this description is made only on ring 11 for'engaging the. ends of rods 9. The others by. way of example and not .as a limitation of the scope endr'of ther rods 9' are positioned, by ring 'i2 'secured to or' my invention as set forth in the objects thereof and element 13 "formingone or" the iris loadinggelements Of in the accompanying-claims. transmission -line 8. I claim:

Radio frequency wave energy to be amplified is coupled l. In a traveling .wave electron discharge device of the f by means of inputA terminal 1d to thelend 'oi helical `line type wterein interactiontalreslplace between theelectrons.. 7 adjacent electron 3. "The waveenergy is then of an electron beam and wave energy .propagatedon a'. propagated down helical line 7 for interaction. with theV slow wave propagating structure disposed in juxtapositlon electrons of .the electron beam.V The` wave Vpropagated with said electron beam, a slow wave propagatlng strucon helical line 7 is composedV of three components, a 15 ture having an energy wave input terminal v.and an energy steady state wave, a decreasing .vi/ave, and an increasing wave output terminal comprising a helical-type transmiswave. "Attenuation section l5 'is disposed adjacent the sion line coupled to said input terminal, a loaded waveoutput end of helical line 7 to eiect a suppression of guide-type (transmission. line c oupledto said.V output ter-- the steady state .and decreasing waves but' primarily it minal and means to couple` waveV energy betweenv said.v serves to .absorb any waves reflected' back towardth'e l20 helical transmissionlineand said waveguide transmission. 'iputa' Heiical line 7 is preferred to be of the counterline.V "f Y wound type to 'help in suppressing the .backward wave. 2. In a traveling `w/ave electron discharge device of the Aft'erfthe 'forward wave passes attenuation section 15,4 type wherein interaction takes place between the electrons thewsave 'energy is amplified by'portion 16 Vof Yhelical of an electron beam and .wave energypropagated on .a

line 7 prior to coupling. to loaded waveguide S through 25 slow wave propagating structure disposed in juxtapositionn. an arrangement to 'excite .loaded waveguide 8, such .as with saidelectron beam, asiow wave propagating .strucf-.iV

n probezcoupling 17.1 "Hence, loaded waveguide 8 is exture having an energy wave input terminaland anpcnergy. citednly "the" wave energy `on helical Vline' 7 wherein theAV wave outputtenninal comprising. al helical-type transmiswave, energy isincreased to a relatively'liigh power. The sion line having one end thereof coupled to `*said input` .n relativeiyhigh: power is coupledfroni. loaded waveguide terminal; a loaded waveguide-type transmission. line.hav.. r 8 by imeans of wave energy output terminal. means 18. ing one end, thereof coupled to said output terminal, .wave

Hence byernpioying the composite slow wave strucenergy fattenuating' meansv disposed adjacentdhepoint ture 6 or' this .inventiomthe wave energy is amplified in where the other end of said A'helical transmission .line .is helic l line 7 to avalar-:substantially equal to the' limiting in juxtaposition with Ythe other ,end .of said waveguide. valueofafhelical structure in a'shorter length than could 35 transmission line and meansA coupling twave .energyf be-N be accomplished by a loaded waveguide structure. The tween said helical transmissionline and saidwaveguide.. output of helical line 7 is then,` coupled to waveguide 3 transmission' line.. whereinthc 'power of thewave energy at theoutput of 3. Thestrncture according. to claim2, wherein..sa.id... helicalrline/T is increased in power to a relativelyhigh attenuating means isV disposed adjacentsaid Aother...end...; power output. The value of output power of the com- Y. 40 of said helicaltransmission line. posite propagating. structure is comparable in value to 4'. Theistructure according to claim 3, wherein said. thatoi an 'all loaded. waveguide structure, but resulting coupling .means includesa portion of said helical transf. in a shortoverall lengthl since thehelical structure has mission line extending intosaid waveguide,transmission.. a higher gain per unit length than that of the .loaded line ionexcitationthereof with wave energy/on.saidheli-` waveguide structure... cal transmission line.

Referring now to Fig. 2, another form of composite 5. Thefstructure according. to claim 2,wherein. said slow'wave propagating structure 6 is illustrated. The attenuating..means is disposedat said othenendlof saidV4 difference' between structure 6 of Eig; l andstructure 6 helicaltransmission line and at said .other .end .of said..... of Fig. 2 is the means for coupling wave energy between waveguide transmission line. the'flow" and high power transmission: line sections.. 50 6. The structure according to claintS, Wherein..said.. Therefore; the reference characters employed in Fig. 1 coupling means includes saidelectron beam... will'lie employed'for like components in Fig.` 2 and only 7. In atraveling.waveelectron discharge deviceof the the"d-iterences'between' the two embodiments will be dis-y type wherein .interaction takesplacebetween theelcctrons.. cuased hereinbelow .with reference .to Fig. 2. of an electron beamand 'wave energy propagated on aslow.:

Env'eiopei of the' embodiment of Fig. 2 may be `c0m 55 wavepropagating structure disposed'in juxtaposition with:V posed Iof rnctalas illustrated in Fig. l or the envelopes said; electron.beam,.a slow-wave Ipropagating. structure..l may be constructed as shown in Fig. 2 including av metalhaving.. an energy .wave...input terminal and .an .energy lic portion 19 in the 'vicinity of loaded. waveguide 8 and r wave output terminal Acomprising a counterwound helical. dielectric portions Ztlto .complete the vacuumenvelope transmission line .having one endthereof coupled to said... substantially as shown. It is to be understood, however, 00 inputterminaL. an Airis-.loaded.waveguide.transmissionline44 thatthe"'vacunm envelopelmay becompletely dielectric having. one end thereof .coupled to saidoutputterminal, withfthe loaded waveguidev disposed therein.` wave energy attenuating means disposed-adjacent then..y

As mentioned hereinabove, the only'dilerencebetween pointwherethe other end'of said.helicaltransmission.-line;` thecomposite'slow wave structures of Figs. 4l and .2. is is in juxtaposition with theother end of saidfwaveguide f in themeans coupling the energyv from helical line .7. to 35 transmission line and means-coupling wave energy bej.e loaded waveguide 8. In the embodimentof Fig. 2, the... tween said helical Ytransmission line' and .said waveguide.` wave'energy Vis coupled fromy helical line] to loaded transmission line.` u waveguide 8 bythe electron beam .of the device. As is 8. The' .structure .according .to claimJ, wherenesaidf.; knowmthisicanbe done sincethe velectron..beamisdensity attenuating means is disposed adjacent said other end of. modulated by. wave. energj/on'helicalY line? and rthis...70 said.helicalutransmissionline-.andsaidcouplingymeansf.. densityrnodultion of the electron beam will excite. loaded.- includes av portionrof .said helical. transmission lineffexwa-` waveguidefS. The'output section .of helical. line 7 is tending into .the adjacent section of said waveguide-trans terminatedin attenuating material .2i at thefend thereof.: Y mission.: .-lineforexcitation thereof withthe wave"7 energy anch-,theiinputof '.loaded. waveguide: 8 is terminated in on said helicaltrausmission line.;` attenuatingmaterial22..coated .on portionof the -innerq 9. The structure according .to claimo?, whereinaf'saiduti.

attenuating means is disposed at said other end of said helical transmission line and in the iirst section at said other end of said waveguide transmission line and said coupling means includes said electron beam.

10. A composite slow wave propagating structure for wave energy comprising ra helical-type transmission line, a Wave energy input means coupled to one end of said helical transmission line, a loaded waveguide-type transmission line, a wave energy output means coupled to one end of said waveguide transmission line, and means to` couple Wave energy between the other end of said helical transmission line and the other end of saidwaveguide transmission line. Y n

1l. A composite slow wave propagating structure for wave energy comprising a counterwound helical transmission line, a wave energy input means coupled to one end of said helical transmission line, an iris-loaded waveguide transmission line, a wave energy output means coupledto one end of said waveguide transmission line, and means to couple wave energy between the other end of said helical transmission line and the other end of said waveguide transmission line.

l2. A traveling wave electron discharge device comprising a vacuum envelope, a collector electrode disposed adjacent one end of said envelope, a means to project an electron beam along a given path'toward saidcollector electrode disposed adjacent the other end of said envelope,

a wave energy propagating structure disposed in interacting relation with the electrons of said electron beam including a helical-type transmission line extending along said path from a point adjacent said electron beam projecting means lto a point intermediate said electron beam projecting means and said collector electrode, a loaded waveguide-type transmission line extending along said path from a point adjacent said intermediate point to a point adjacent said collector electrode, wave energy 1 attenuating means disposed adjacent said intermediate point, and means to couple wave energy between said helical transmission line and said waveguide transmission line, input wave energy terminal means in coupled relation with said helical. transmission line adjacent said electron beam projecting means, and output wave energy terminal means in coupled relation with said waveguide transmission line adjacent said collector electrode.

13. A discharge device according to claim 12, wherein said attenuating means is disposed in juxtaposition with said helical transmission line adjacent said intermediate point and said coupling means includes a portion of said helical transmission line extending into said waveguide transmission line for excitation thereof with the wave energy on said helical transmission line.

14. A discharge device according to claim 13, wherein said attenuating means is disposed in juxtaposition with said helical transmission line and said waveguide transmissionrline immediately adjacent said intermediate point and said coupling means includes said electron beam.

15. A traveling wave electron discharge device comprising a vacuum envelope, a collector electrode disposed adjacent one end of said envelope, a means to project an electron beam along a given path toward said collector electrode disposed adjacent the other end of said envelope, a wave energy propagating structure disposed in interacting relation with the electrons of said electron beam including a counterwound helical transmission line extending along said path from a point adjacent said electron beam projecting means to a point intermediate said electron beam projecting means and said collector electrode, an iris-loaded waveguide transmission line extending along said path from a point adjacent said intermediate point to a point adjacent said collector electrode, wave energy attenuating means disposed in juxtaposition with said helical transmission line adjacent said intermediate point andaportion of said helical transmission line extending into said waveguide transmission line for excitation thereof with Wave energy on said helical transmission line, input wave energy terminal means in coupled relation with said helical transmission line adjacent saidV electron beam projecting means, and output wave energy terminal means in coupled relation with said waveguideA acting relation with the electrons ofvsaid electron beaml including a counterwound helical transmission line extending' along said path from a point adjacent said electron beam projecting means to a point intermediate said electron beam projecting means and said collector electrode, an iris-loaded waveguide transmission line extending along said path from a point adjacent said intermediate point to a point adjacent said collector electrode,

wave energy attenuating means disposed in juxtaposition with said helical transmission line and said waveguide transmission line immediately adjacent said intermediate point, yand said electron beam coupling wave energy between said helical transmission line and said waveguide transmission line, input wave energy terminal means in coupled relation with said helical transmission line 'adja-r cent said electron beam projecting means, and output wave energy terminal means in coupled relation with said waveguide transmission line adjacent said collector electrode.

References Cited in the le of this patent y UNITED STATES PATENTS Landauer Feb. 5, 1952 2,584,597 v 2,636,948 Pierce i Apr. 2s, 1953 f 2,760,161 Cutler Aug. 21, 1956 2,824,257 Branch F66. 1s, 195s 2,836,758 Chodorow May 27, 1958 FOREIGN PATENTS 943,236 Germany May 17, 1956 

